The invention relates to an ophthalmological apparatus, in particular a so-called slit lamp apparatus in accordance with the preamble of patent claim 1, and to an arrangement in accordance with patent claim 10.
A slit lamp apparatus as ophthalmological apparatus is known for example from Haag-Streit, under the designation xe2x80x9cOriginal slit lamp 900 BMxe2x80x9d. A further slit lamp apparatus is described in the European patent application EP-A 0 916 306 (EP-98 810 895.7).
It is an object of the invention to provide an ophthalmological apparatus, in particular a so-called slit lamp apparatus, which, compared with the known apparatuses, provides the treating or examining ophthalmologist with a significantly greater area of application in one and the same apparatus with extremely simple operation. Furthermore, the intention is for this apparatus to be able to be integrated into an arrangement for eye treatment.
The way in which the object is achieved is the subject matter of patent claim 1.
Specifically, compared with the known apparatuses, the invention no longer has a mechanical diaphragm by means of which the geometrical cross-sectional form of an examining light beam can be adjusted. According to the invention, then, the cross-sectional intensity distribution of a light stria (slit) required for the eye examination is performed by means of a so-called planar light modulator. The adjustable optical properties of this planar light modulator are adjusted or altered in a simple manner at predeterminable and freely selectable locations by means of the procedures presented below. The optical properties over the irradiatable region of the planar light modulator can then be alteredxe2x80x94under remote controlxe2x80x94in such a way that a desired optical structure with predeterminable optical properties is achieved. This optical structure then alters a light beam incident on it either in transmission or reflection in accordance with the required intensity distribution. This different intensity distribution generally has the same effect on or in the eyexe2x80x94except for differences presented belowxe2x80x94as the mechanical diaphragms used heretofore. The geometrical cross section of an illumination beam can now be rapidly altered in a simple manner. However, it is likewise possible to generate from it in a simple manner a light band, an arrangement of lines, an arrangement of points or some other optical figures for the eye illumination or examination, i.e. to change its intensity distribution.
Depending on the planar light modulator (described below) used, it is possible to generate intensity distributions, i.e. images, whose individual image elements have a raster or are raster-free, a raster, analogously to general printing technology, being understood as an arrangement of equidistant points. The arrangement of spaced-apart points may, of course, be different; but it is always identical in one and the same image. A raster is obtained whenever image elements in a planar light modulator are activated by matrix-like, in general electrical driving. However, in this case a raster is not understood as an arrangement of points as is used below for determining imaging errors of the eye.
With a planar light modulator operating in a raster-free manner, in contrast to a planar light modulator operating with a raster, it is possible to generate e.g. areal image elements with a constant optical property without internal structure.
A raster-free generation of image elements is achieved e.g. when a corresponding image is xe2x80x9cwrittenxe2x80x9d or xe2x80x9cimpressedxe2x80x9d optically with a light or laser beam or a projected imaging into the planar light modulator. In this case, depending on their intensity distribution over the beam cross section, the xe2x80x9cwriting beamsxe2x80x9d can be moved in a manner overlapping one another in the beam edge region in such a way that an image element with constant luminance can be generated by the area region respectively written to. It goes without saying that variable luminances can also be generated. In addition to the optical figures in a bright/dark representation mentioned below, it is also possible to generate figures with different gray tones.
A differentiation in use between these two types of planar light modulators is important since different perceptions can be generated in the eye by this means and different test methods can thus also be performed on the eye. Specifically, for an observer to be examined, a completely different impression is given in the case of intrinsically rastered optical figures and figures with a raster-free intensity profile.
Hitherto, in the case of the slit lamp apparatuses known for examinations, the person skilled in the art of ophthalmology had always proceeded from an adjustable mechanical diaphragm. It was obvious to use such a diaphragm since the intention was in each case to image a light band with a surrounding dark region on the eye or within it, and this was generated precisely by means of a mechanical diaphragm, as e.g. also in the case of cameras. If, in a departure from a simple light band, for keratometric measurements, the intention was to image geometrical structures on or in the eye, then in this case, to, as described in U.S. Pat. No. 5,418,582, mechanical diaphragms with completely translucent and completely blocking diaphragm regions were used. By means of the invention described below, in a simple manner, without any change in hardware, it is possible for example also to image the geometrical structure generated with the ring cone of U.S. Pat. No. 5,418,582, in addition to a customary light band imaging.
By means of a planar light modulator of this type, it is possible, then, to generate a xe2x80x9clight bandxe2x80x9d having dimensions and an intensity distribution as corresponds to the conventional one, which was performed by means of a mechanically adjustable diaphragm. Over and above such a xe2x80x9clight bandxe2x80x9d, it is now possible, however, to generate any desired intensity distributions and figures. It is now possible to generate e.g. a multiplicity of light bands which are parallel to one another or are at any desired angles with respect to one another. Moreover, it is possible to generate annuli, full circles, Placido rings, cross gratings, . . .
Since image information for a video recording unit can be extracted from the observation beam path, as described, in particular, in EP-A 0 916 306 (EP-98 810 895.7) already mentioned, automatic evaluation can, moreover, be performed. The original image can be compared with its projection on curved areas such as the cornea and retina. From this comparison, the corresponding curvatures can then be determined automatically by an evaluation unit.
The apparatus according to the invention is thus excellently suitable, in addition to the examinations and treatment methods of a slit lamp apparatus already known, for cornea thickness measurement, for creation of a 2D or 3D fundus profile, for cornea topography, for fundus topography,